One of the fundamental questions confronting battery research regards the mechanism of the solid-electrolyte interphase's (SEI) formation. Typically, the SEI is formed during the initial charging of a battery, and when formed, it protects the anode from reacting with the electrolyte while allowing Li ions to migrate to and from the anode. This process contains three general reactions: 1) Li intercalation; 2) electrochemical reduction of electrolyte; and 3) chemical reduction of electrolyte by reduced Li.
Increasing the amount of Li is a known strategy for increasing performance and cycle life of re-chargeable Li-ion batteries. The excess lithium is used in preparation and maintenance of the solid electrolyte interphase (SEI) formed primarily at the anode surface during cycling. Industry typically accomplishes this by increasing the amount of cathode material or using lithium-rich materials. This strategy results in a significant amount of wasted cathode material, which decreases the energy density of the battery. Strategies for increasing the lithium content in batteries by producing pre-lithiated anode materials have been proposed, however, pre-lithiation presents inherent difficulties: 1) pre-lithiated materials are only 0.1-0.2 V more positive than Li metal and therefore are highly reductive; 2) they spontaneously react with most organic solvents, battery electrolytes and gaseous O2 and H2O exothermically; and 3) they produce a passivation layer upon contact with the aforementioned chemicals of lithium carbonate, fluoride and oxide, and polycarbonates. Confronting processing problems of reactive pre-lithiated anodes is important for providing alternate means to improve battery performance by increasing Li loading or allowing for SEI synthesis.